Multiple needle attempts to gain a muscle twitch or a paresthesia for a classical supraclavicular brachial plexus block can increase the risks of nerve damage or pain. The aims of this study were to obtain reliable clinical data on ultrasound-guided supraclavicular blocks, demonstrate the higher success rate and fewer complications, and design an injection method for patients whose brachial plexus can not be located.

105 patients received an ultrasound-guided supraclavicular block. 40 ml of 1% mepivacaine was injected without a muscle twitch or paresthesia. The groups were divided into two groups - Group A (n = 92, patients who had visible brachial plexus) and Group B (n = 13, patients whose brachial plexus can't be located). After the blocks, the clinical characteristics such as the success rate, the time to onset, the extent of the sensory block, and occurrence of complications were evaluated.

The Success rate of Group A (98.9%) was higher than that of Group B (84.6%) (P < 0.05). The overall success rate was 97.1%. All patients could be operated on under sedation. The time to onset of Group A (12.6 ± 4.4 min) was shorter than that in Group B (23.1 ± 5.1 min) (P < 0.05). The overall time to onset was 13.8 ± 5.5 min. There were no serious complications such as pneumothorax.

An ultrasound-guided supraclavicular block is very effective in even patients whose brachial plexus can not be located.